Anti-Stokes and Stokes photoluminescence in non-uniform GaAs-based quantum wells

The intensity distribution of the anti-Stokes photoluminescence (AS-PL) signal has been investigated in a quantum heterostructure containing several GaAs-based quantum wells (QWs) of different thickness. We observe four emission bands at different energies, which originate from the spatially different positions of the QWs in the heterostructure. When the photon energy of the excitation is tuned to the QW with the lowest emission energy, we detect a clear resonant enhancement of the AS-PL signal of the exciton state highest in energy, which belongs to the QW located in close proximity. This observation implies that the capture of non-equilibrium carriers within the QWs plays a very important role for determination of the AS-PL intensity distribution.